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The electrical conductivity, the osmotic coefficient, the apparent molar volume, and the enthalpy of dilution of aqueous solutions of the lithium and cesium salts of fullerenehexamalonic acid, C66(COOH)12, were measured at 25 degree Celcius in a wide concentration range. A semiquantitative agreement was observed when the experimental data was compared with predictions of the spherical cell model.

It has been possible to make transport and equilibrium studies with aqueous solutions of the sodium salt of fullerenehexamalonic acid, C66(COONa)12. The experimental data were compared with the theoretical predictions based on the solution of the Poisson-Boltzmann equation for the spherical cell model.

A study was conducted on the physicochemical properties of the fullerenehexamalonic acid Th-C66(COOH)12. Chemical shifts were assessed using 13C nuclear magnetic resonance analysis. Some of the properties evaluated include sodium salt, solubility, electrical conductivity, osmotic coefficient and apparent molar volume. Fullerenehexamalonic acid behaved as a diprotic acid. A second carboxylic group with an estimated pK2 value of 5.5 was identified. Moreover, the data suggest that the salts of C66(COOH) with strong bases will behave like highly charged strong electrolytes.

The indirect moving boundary method is used for determining the transport number of the macroion constituent in aqueous solutions of fullerenehexamalonic acid ([C.sub.66][(COOH).sub.12]) and its lithium, sodium, cesium and calcium salts. The fraction of counterions bound to the macroion is obtained and the degrees of immobilization obtained from transport experiments are shown to be lower than those derived from equilibrium properties.